Introduction. Partial knee arthroplasty (PKA) has demonstrated the potential to improve patient satisfaction over total knee arthroplasty. It is however perceived as a more challenging procedure that requires precise adaptation to the complex mechanics of the knee. A recently developed PKA system aims to address these challenges by anatomical, compartment specific shapes and fine-tuned mechanical instrumentation. We investigated how closely this PKA system replicates the balance and kinematics of the intact knee. Materials and Methods. Eight post-mortem human knee specimens (age: 55±11 years, BMI: 23±5, 4 male, 4 female) underwent full leg CT scanning and comprehensive robotic (KUKA KR140 comp) assessments of tibiofemoral and patellofemoral kinematics. Specimens were tested in the intact state and after fixed bearing medial PKA. Implantations were performed by two experienced surgeons. Assessments included laxity testing (anterior-posterior: ±100 N, medial-lateral: ±100 N, internal-external: ±3 Nm, varus- valgus: ±12 Nm) under 2 compressive loads (44 N, 500 N) at 7 flexion angles and simulations of level walking, lunge and stair descent based on in-vivo loading profiles. Kinematics were tracked robotically and optically (OptiTrack) and represented by the femoral flexion facet center (FFC) motions. Similarity between intact and operated curves was expressed by the root mean square of deviations (RMSD) along the curves. Group data were summarized by average and standard deviation and compared using the paired Student's T-test (α = 0.05). Results. During the varus-valgus balancing assessment the medial and lateral opening of the PKAs closely resembled the intact openings across the full arch of flexion, with RMSD values of 1.0±0.5 mm and 0.4±0.2 mm respectively. The medial opening was nearly constant across flexion, its average was not statistically different between intact (3.8±1.0 mm) and PKA (4.0±1.1 mm) (p=0.49). Antero-posterior envelope of motion assessments revealed a close match between the intact and PKA group for both compression levels. Net rollback was not statistically different, either under low compression (intact: 10.9±1.5 mm, PKA: 10.7±1.2, p=0.64) or under high compression (intact: 13.2±2.3 mm, PKA: 13.0±1.6 mm, p=0.77). Similarly, average laxity was not statistically different, either under low (intact: 7.7±3.2 mm, PKA: 8.6±2.5 mm, p=0.09) or under high (intact: 7.2±2.6 mm, PKA: 7.8±2.2 mm, p=0.08) compression. Activities of daily living exhibited a close match in the anterior-posterior motion profile of the medial condyle (RMSD: lunge: 2.2±1.0 mm, level walking: 2.4±0.9 mm, stair descent: 2.2±0.6 mm) and lateral condyle (RMSD: lunge: 2.4±1.4 mm, level walking: 2.2±1.4 mm, stair descent: 2.7±2.0 mm). Patellar medial-lateral tilt (RMSD: 3.4±3.8°) and medial-lateral shift (RMDS: 1.5±0.6 mm) during knee flexion matched closely between groups. Conclusion. Throughout the comprehensive functional assessments the investigated PKA system behaved nearly identical to the intact knee. The small residuals are unlikely to have a clinical effect; further studies are necessary as cadaveric studies are not necessarily indicative of clinical results. We conclude that PKA with anatomical, compartment specific shapes and fine-tuned mechanical instrumentation can be adapted precisely to the complex mechanics of the knee and replicates intact knee balance and kinematics very closely

INTRODUCTION

There is strong current interest to provide reliable treatments for one- and two-compartment arthritis in the cruciate-ligament intact knee. An alternative to total knee arthroplasty is to resurface only the diseased compartments with discrete compartmental components. Placing multiple small implants into the knee presents a greater surgical challenge than total knee arthroplasty, and it is not certain natural knee mechanics can be maintained. The goal of this study was to compare functional kinematics in cruciate-intact knees with either medial unicondylar (mUKA), mUKA plus patellofemoral (mUKA+PF), or bi-unicondylar (biUNI) arthroplasty using discrete compartmental implants with preparation and placement assisted by haptic robotic technology.

Background

More and more patients with end-stage knee OA are treated with total knee replacements (TKR). A modern TKR (Persona PS system, Zimmer Inc.) was designed with the hope to improve fit by providing additional sizing options on the femur and tibia. To date, there is very little information regarding the knee strength and knee mechanics during gait after the TKR. Furthermore, as a great percentage of knee OA patients have OA limited in one knee compartment and in the patellofemoral joint, a bi-compartmental knee replacement (BKR) (iDUO system, ConforMIS Inc.) was designed to treat OA at these affected areas. The BKR re-creates the individual's knee shape while correcting for any deformity. In addition, the BKR procedure results in less bone loss and retains the cruciate ligaments. To date, the influence of the BKR on knee strength and knee mechanics remains unknown. The purpose of the study was to evaluate knee strength and mechanics during level walking after the TKR and BKR surgeries.

Not all degenerative knees need a total knee replacement. Over the last few decades we have shifted our surgical treatment of end-stage osteoarthritis (OA) of the knee to a “compartmental approach” resulting in approximately half of end-stage OA knees receiving a partial knee replacement. Of these an emerging procedure is isolated lateral compartment replacement with the indications being isolated bone-on-bone osteoarthritis or avascular necrosis of the lateral compartment of the knee. Associated significant patellofemoral disease and inflammatory arthritis are contraindications. The purpose of this study is to present the indications, surgical technique, and early outcome of lateral partial knees from our institution. From Aug 2011 until June 2017 we have performed 3,548 knee arthroplasties. Of these 147 were fixed bearing lateral partial knee replacements via a lateral parapatellar approach (4%), 1,481 medial partial knee replacements (42%), and 1,920 total knee replacements (54%). The average age was 66 years old and 76% were female. Average follow-up in the lateral partials was 1.3 years (range 0.5 years to 6 years). Knee Society Scores improved from 41 (pre-op) to 86 points (post-op). Range of motion improved from 6 – 113 degrees (pre-op) to 0 – 123 degrees (post-op). No knees were revised to a TKA. One knee required I&D for traumatic wound dehiscence. This is the largest single center series of lateral partial knee replacements. We have observed this cohort to have more female patients and gain additional range of motion compared to our historic cohorts of TKA's. Longer-term follow-up is needed for determination of implant and unreplaced compartment survivorship. We believe the lateral partial knee replacement to be a viable option for isolated lateral compartment disease in approximately 4% of patients

Advances in algorithms developed with sensor data from smart phones demonstrates the capacity to passively collect qualitative gait metrics. The purpose of this feasibility study was to assess the recovery of these metrics following joint reconstruction. A secondary data analysis of an ethics approved global, multicenter, prospective longitudinal study evaluating gait quality data before and after primary total knee arthroplasty (TKA, n=476), partial knee arthroplasty (PKA, n=139), and total hip arthroplasty (THA, n=395). A minimum 24 week follow-up was required (mean 45±12, range 24 - 78). Gait bouts and gait quality metrics (walking speed, step length, timing asymmetry, and double support percentage) were collected from a standardized smartphone operating system. Pre- and post-operative values were compared using paired-samples t-tests (p<0.05). A total of 595 females and 415 males with a mean age of 61.9±9.3 years and mean BMI of 30.2±6.1 kg/m. 2. were reviewed. Walking speeds were lowest at post-operative week two (all, p<.001). Speeds exceeded pre-operative means consistently by week 21 (p=0.015) for PKA, and week 13 (p=0.007) for THA. The average weekly step length was lowest in post-operative week two (all, p<0.001). PKA and THA cases achieved pre-operative step lengths by week seven (p=0.064) and week 9 (p=0.081), respectively. The average weekly gait asymmetry peaked at week two post-operatively (all, p <0.001). Return to pre-operative baseline asymmetry was achieved by week 11 (p=0.371) for TKA, week six (p=0.541) for PKA, and week eight (p=.886) for THA. Double limb support percentages peaked at week two (all, p<0.001) and returned to pre-operative levels by week 24 (p=0.089) for TKA, week 12 (p=0.156) for PKA, and week 10 (p=0.143) for THA. Monitoring gait quality in real-world settings following joint reconstruction using smartphones is feasible, and may provide the advantage of removing the Hawthorne effect related to typical gait assessments and in-clinic observations

Traditional procedures for orthopedic total joint replacements have relied upon bone cement to achieve long-term implant fixation. This remains the gold standard in number of procedures including TKR and PKR. In many cases however, implants fixed with cement have proven susceptible to aseptic loosening and 3. rd. body wear concerns. These issues have led to a shift away from cement fixation and towards devices that rely on the natural osteoconductive properties of bone and the ability of porous-coated implants to initiate on-growth and in-growth at the bone interface, leading to more reliable fixation. To facilitate long-term fixation through osseointegration, several mechanical means have been utilized as supplemental mechanism to aid in stabilizing the prostheses. These methods have included integrated keels and bone screws. The intent of these components is to limit implant movement and provide a stable environment for bone ingrowth to occur. Both methods have demonstrated limitations on safety and performance including bone fracture due keel induced stresses, loosening due to inconsistent pressfit of the keel, screw-thread stripping in cancellous bone, head-stripping, screw fracture, screw loosening, and screw pullout. An alternative method of fixation utilizing blade-based anchoring has been developed to overcome these limitations. The bladed-based fixation concept consists of a titanium alloy anchor with a “T-shaped” cross-section and sharped-leading end that can be impacted directly into bone. The profile is configured to have a bladed region on the horizontal crossbar of the “T” for engagement into bone and a solid rail at the other end to mates with a conforming slot on the primary body of the prosthesis. A biased chisel tip is added to the surface of the leading blade edge to draw the bone between the anchor's horizontal surface and surface of the implant, thus generating a compressive force at the bone-to-prothesis interface. The anchoring mechanism has been successfully been integrated into the tibial tray component of a partial knee replacement; an implant component that has a clinical history of revision due to loosening. A detailed investigation into the pulloff strength, wear debris generation, compressive-force properties, and susceptibility to tibial bone fracture was carried out on the anchor technology when integrated in a standard tibial tray of a partial knee replacement. When tested in rigid polyurethane bone foam (Sawbones, Grade 15) the pulloff strength of the construct increased by 360% when utilizing the anchor. The tibial tray and anchor construct were cycled under compressive loading and demonstrated no evidence of interface corrosion or wear debris generation after 1 million cycles. In addition, the anchor mechanism was shown to generate 340N of compressive force at the tibial tray-to-bone interface when evaluated with pressure sensitive film (Fuji Prescale, Medium Grade). Finally, the ultimate compressive load to induce tibial fracture was shown to increase by 17% for the anchored tray as compared to a traditional keeled tray when tested in an anatomic tibial sawbones model; and by 19% when evaluated in human cadaveric tibias. For any figures or tables, please contact authors directly

Refinement of surgical techniques, anaesthesia protocols, and patient selection have facilitated this transformation to same day discharge for arthroplasty care, most notably Partial Knee Arthroplasty (PKR). The trend for early discharge has already happened for procedures formerly regarded as “inpatient” procedures such as upper extremity surgery, arthroscopy, ACL reconstruction, foot and ankle procedures, and rotator cuff repair. Our program began focused on Partial Knee Arthroplasty (PKA) and has now expanded to primary TKA and THA, and select revision cases. Over the past few years we have performed 1,230 Knee Arthroplasty procedures with no readmissions for pain control. Average age and age range is identical to our inpatient cohort for our partial knee cases. Patient selection is based on medical screening criteria and insurance access. PKA is the ideal procedure to begin your transition to the outpatient space. We currently perform medial PKA, lateral PKA, and patellofemoral arthroplasty as outpatient cases. The program centers on the patient, their family, home recovery, pre-operative education, efficient surgery, and represents a shift in the paradigm of arthroplasty care. It can be highly beneficial to patients, surgeons, anaesthesia, facility costs, and payors as arthroplasty procedures shift to the outpatient space. Perhaps the most significant developments in joint replacement surgery in the past decade have been in the area of multimodal pain management. This has reduced length of stay in the inpatient hospital environment opening the opportunity for cost savings and even outpatient joint replacement surgery for appropriately selected patients. The hallmark of this program is meticulous protocol execution. Pre-emptive pain control with oral anti-inflammatory agents, gabapentin, regional anesthetic blocks that preserve quad function for TKA (adductor canal block) and pericapsular long acting local anesthetics with the addition of injectable ketorolac and IV acetaminophen are key adjuncts. Over the past two years utilizing this type of program over 60% of our partial knee replacement patients are now returning home the day of surgery. Concerns over readmission are appropriate. The rates of complications and readmissions are less than our inpatient cohort in appropriately selected cases with a standardised care map. We believe this brings the best VALUE to the patients, surgeons, and the arthroplasty system

Perhaps the most significant developments in joint replacement surgery in the past decade have been in the area of multimodal peri-operative management reducing pain, nausea, and length of stay leading to outpatient joint replacement surgery with recovery at home. The surgical procedures included in the outpatient program have expanded from Partial Knee Arthroplasty to Primary TKA, Primary THA, and selected revision cases. Emerging data demonstrate safety, reduced cost, and reduced resources. Since 2011, we helped develop and implement an outpatient program as part of 76 participating physician-owned ambulatory facilities in 19 states − 19,415 joint replacements have been performed. The cohort included 6,146 TKA, 5,102 THA, 7,227 partial knee replacements, and 940 revisions and TSA. Patients had a mean age of 58 years and 50% of the patients were female; 97% of patients were discharged same day, the deep infection rate was 0.2%, and the readmission rate was 0.3%. The outpatient program centers on the patient needs, family engagement, essentials of home recovery, pre-operative education, efficient surgery, and a surgeon controlled environment with highly standardised care. This is a distinct shift in today's health care environment, which has seen the expansion of regulatory demands; focus on Electronic Health Records (EHR), and distractions from real discussions of demonstrated value creation. The future is bright for both ASC and hospital development of successful outpatient joint replacement program for patients and surgeons alike

Total knee replacement (TKR) is considered the “gold standard” treatment for advanced osteoarthritis (OA) of the knee with good survivorship and functional outcomes. However up to 20% of patients undergoing TKR may have unicompartmental disease only. Treatment options for medial compartment arthritis can include both unicompartmental knee replacements (UKR) and TKR. While some surgeons favor TKR with a proven track record, others prefer UKR due to more normal joint kinematics, better proprioception and better motion. There is also a higher rate of return to sports amongst patients with UKR compared to TKR. When considering all knee procedures, partial knee replacements account for 7–9%, primary TKRs for 83–88%, and revision knee replacements for 5–8%. Unicompartmental Knee Replacements comprise more than 90% of all partial knee replacement procedures. Proponents of UKR cite as advantages the preservation of normal knee kinematics, lower peri-operative morbidity, blood loss and infection risk compared with TKRs, as well as accelerated patient rehabilitation and recovery. However, partial knee replacements have a higher rate of revision than TKRs. This may be partly because they are inserted in patients with higher expectations, and partly because they are easier to revise. As a result, the volume of UKRs implanted has diminished over time and continues to decline. We compared patient reported outcomes, satisfaction and perception of normality of the knee post-operatively between UKR and TKR. A single unit and single surgeon series of patients were recruited. Data was collated for 68 well-matched patients with more than 24 months follow-up. UKR was undertaken in patients with isolated medial compartment osteoarthritis; stable ACL and less than grade 3 lateral patellar changes of the Outerbridge classification. TKR was undertaken for the rest. The patients were assessed with validated knee scores including the Total Knee Function Questionnaire (TKFQ) which focuses on recreational and sporting outcomes as well as activities of daily living (ADL). Patient satisfaction and perception of knee normality was measured on a visual analogue scale. Thirty-four patients with a TKR and 34 patients with a UKR were analyzed. The average ages in the TKR and UKR groups were 69.25 and 67.26 years, respectively. The patients were well-matched for demographics and had equivalent pre-operative morbidities and scores. The UKR group had better WOMAC (p=0.003), SF36 (physical: p<0.001 mental: p=0.25), Oxford knee (p<0.001) and Knee Society scores (p=0.002, function: p<0.001). The UKR group showed better outcomes in the TKFQ including exercise and sport (p= 0.02), movement and lifestyle (p=0.02) and the ADL (p=0.002). There was, however, no difference in patient satisfaction scores (p=0.41) and perception of how normal the knee felt between the two groups (p=0.99). A UKR procedure confers better functional outcome in terms of recreation and sport compared to TKR procedures. While UKR is an appropriate choice in the elderly yet active patient with unicompartmental knee arthritis, satisfaction is similar to that of patients with a TKR reflecting higher pre-operative expectations. We believe that in appropriate centers, the UKR procedure is associated with excellent outcomes. UKR should have a secure place in the knee arthroplasty armamentarium provided current knowledge regarding patient selection and surgical technique is followed

Refinement of surgical techniques, anesthesia protocols, and patient selection has facilitated this transformation to same day discharge for arthroplasty care, most notably Partial Knee Arthroplasty (PKA). The trend for early discharge has already happened for procedures formerly regarded as “inpatient” procedures such as upper extremity surgery, arthroscopy, ACL reconstruction, foot and ankle procedures, and rotator cuff repair. Our program began focused on PKA and has now expanded to primary TKA and THA, and select revision cases. Over the past few years we have performed 1,230 knee arthroplasty procedures with no readmissions for pain control. Average age and age range is identical to our inpatient cohort for our partial knee cases. Patient selection is based on medical screening criteria and insurance access. PKA is the ideal procedure to begin your transition to the outpatient space. We currently perform medial PKA, lateral PKA, and patellofemoral arthroplasty as an outpatient. The program centers on the patient, their family, home recovery, preoperative education, efficient surgery, and represents a shift in the paradigm of arthroplasty care. It can be highly beneficial to patients, surgeons, anesthesia, facility costs, and payors as arthroplasty procedures shift to the outpatient space. Perhaps the most significant developments in joint replacement surgery in the past decade have been in the area of multimodal pain management. This has reduced length of stay in the inpatient hospital environment opening the opportunity for cost savings and even outpatient joint replacement surgery for appropriately selected patients. The hallmark of this program is meticulous protocol execution. Preemptive pain control with oral anti-inflammatory agents, gabapentin, regional anesthetic blocks that preserve quad function for TKA (adductor canal block) and pericapsular long acting local anesthetics with the addition of injectable ketorolac and IV acetaminophen are key adjuncts. Over the past two years utilizing this type of program over 60% of our partial knee replacement patients are now returning home the day of surgery. Concerns over readmission are appropriate. The rates of complications and readmissions are less than our inpatient cohort in appropriately selected cases with a standardised care map. We believe this brings the best VALUE to the patients, surgeons, and the arthroplasty system

Purpose. Evaluation of status of collateral ligament & prediction of post-op alignment is important for partial knee replacement because during UKA the ligament can't be released & overcorrection or severe varus alignment result in poor clinical result. Evaluation of ligament could be done with valgus stress or distraction. The authors compare the stress view & distractive CT scanogram. to know the effectiveness regarding the prediction of final alignment. Material & Method. 19 knee from the 16 people receiving partial knee replacement was studied, we measure the anatomical axis &mechanical axis of the valgus stress view & distractive CT scanogram & post-operative whole leg radiogram. Result. anatomic axis in preoperative radiograph of a 30-degree valgus load was 7.31 ± 3.33, that of full-length radiograph of postoperative period was 3.11 ± 2.12, there was a significant difference between both groups (p = 0). Anatomic axis in preoperative CT anatomical valgus axis was 2.36 ± 2.04 & that of full-length radiograph of postoperative period was 3.11 ± 2.12, there were not significantly different. (P = 0.209). mechanical axis in preoperative of distraction CT scanogram were 4.15 ± 2.23 & that of post-op full length radiogram was 3.43 ± 2.42,& there were no significant difference between both groups. (P = 0.314) displacement of the mechanical axis of the surgery was 29.27 ± 14.08% in CT,& that of post-op full length radiogram was 34.45 ± 11.9%, there was no significant difference in both groups. (P = 0.261). Conclusion. InPartial knee replacement, distractive CT scanogram effectively predict the post-operative alignment, & valgus stress view show the overcorrected alignment

Tibial and femoral component malalignment is poorly tolerated in uni- and bi-compartmental knee replacement. Poor outcomes may still occur while using navigation or robotic-assisted bone preparation, which currently require surgeon assessment to establish a preoperative plan for implant placement. Choosing where to place partial knee replacement components is a challenging task that depends on complicated interactions between patient variability and implant design. We developed a patient-customizable knee model that can assist surgeons by providing a quantitative measure of knee laxity. In order to build upon previous knee modeling efforts and to demonstrate the technique, three-dimensional femur and tibia bone and articular cartilage geometries were obtained from the OpenKnee finite element repository (. https://simtk.org/home/openknee. ). Generic, patient-customizable transversely isotropic, fibril-reinforced cruciate and collateral ligament models, which allow for bone-to-ligament, cartilage-to-ligament, ligament-to-ligament interaction, were substituted into the model (Figure 1). This reduces the dependency on expensive and time-consuming MRI segmentation required to recreate soft-tissue geometries. Ligament pre-tensioning and insertion and origin sites (approximated as elliptical regions fit to the bone surface) can be tuned to match a patient's passive knee kinematics. The model was run through a series of simulated passive flexion paths. At each degree of flexion, combinations of anterior-posterior and medial-lateral forces as well as internal-external and varus/valgus moments were applied and the resulting joint kinematics were recorded. These results represent the passive envelope of knee motion, which is used to characterize knee laxity. An optimization framework was developed to iteratively tune the cruciate ligament model to match a virtual set of passive loading conditions. A majority of preoperative planning techniques only monitor geometric targets such as flexion and extension gaps, limb alignment, restoration of the joint line, and tibial component slope. Patient-customized knee models can be tuned to quantify post-operative knee laxity and identify the range of tolerable alignment of partial knee replacement components. Future work will employ in-vitro testing to validate the capability of the model to identify patient-specific cruciate ligament parameters

Combined Partial Knee Arthroplasty (CPKA) is a promising alternative to Total Knee Arthroplasty (TKA) for the treatment of multi-compartment arthrosis. Through the simultaneous or staged implantation of multiple Partial Knee Arthroplasties (PKAs), CPKA aims to restore near-normal function of the knee, through retention of the anterior cruciate ligament and native disease-free compartment. Whilst PKA is well established, CPKA is comparatively novel and associated biomechanics are less well understood. Clinically, PKA and CPKA have been shown to better restore knee function compared to TKA, particularly during fast walking. The biomechanical explanation for this superiority remains unclear but may be due to better preservation of the extensor mechanism. This study sought to assess and compare extensor function after PKA, CPKA, and TKA. An instrumented knee extension rig facilitated the measurement extension moment of twenty-four cadaveric knees, which were measured in the native state and then following a sequence of arthroplasty procedures. Eight knees underwent medial Unicompartmental Knee Arthroplasty (UKA-M), followed by patellofemoral arthroplasty (PFA) thereby converting to medial Bicompartmental Knee Arthroplasty (BCA-M). In the final round of testing the PKA implants were removed a posterior-cruciate retaining TKA was implanted. The second eight received lateral equivalents (UKA-L then BCA-L) then TKA. The final eight underwent simultaneous Bi-Unicondylar Arthroplasty (Bi-UKA) before TKA. Extensor efficiencies over extension ranges typical of daily tasks were also calculated and differences between arthroplasties were assessed using repeated measures analysis of variance. For both the medial and lateral groups, UKA demonstrated the same extensor function as the native knee. BCA resulted in a small reduction in extensor moment between 70–90° flexion but, in the context of daily activity, extensor efficiency was largely unaffected and no significant reductions were found. TKA, however, resulted in significantly reduced extensor moments, leading to efficiency deficits ranging from 8% to 43% in flexion ranges associated with downhill walking and the stance phase of gait, respectively. Comparing the arthroplasties: TKA was significantly less efficient than both UKA-M and BCA-M over ranges representing stair ascent and gait; TKA showed a significant 23% reduction compared to BCA-L in the same range. There were no differences in efficiency between the UKAs and BCAs over any flexion range and TKA efficiency was consistently lower than all other arthroplasties. Bi-UKA generated the same extensor moment as native knee at flexion angles typical of fast gait (0–30°). Again, TKA displayed significantly reduced extensor moments towards full extension but returned to the normal range in deep flexion. Overall, TKA was significantly less efficient following TKA than Bi-UKA. Recipients of PKA and CPKA have superior functional outcomes compared to TKA, particularly in relation to fast walking. This in vitro study found that both UKA and CPKA better preserve extensor function compared to TKA, especially when evaluated in the context of daily functional tasks. TKA reduced knee extensor efficiency by over 40% at flexion angles associated with gait, arguably the most important activity to maintain patient satisfaction. These findings go some way to explaining functional deficiencies of TKA compared to CPKA observed clinically

Introduction:. Patient expectations have escalated over the past several decades with respect to demand for success with total knee arthroplasty (TKA). It is reported that 15% to 20% of TKA recipients are unsatisfied with their result. Dynamic fluoroscopic studies and gait analyses have demonstrated that patients with TKA do not exhibit normal kinematics. On the other hand, patients with partial knee arthroplasty demonstrate more normal kinematics, thought to be secondary to retention of the anterior cruciate ligament (ACL) along with the posterior cruciate ligament (PCL). While not a new concept, bicruciate-retaining designs in TKA that preserve the natural ligament structure of the knee are drawing renewed interest as an option for patients with higher and more complex activity demand. These designs may result in a more natural kinematic feel as perceived by the patient. In a study of 2313 knees in patients undergoing primary knee arthroplasty at our center, the ACL was observed to be intact in 80% and normal in 53%. Bi-cruciate retaining TKA has recently been re-introduced for use in patients with an intact ACL and PCL. As with the introduction of any new technology into orthopaedic surgery, there is a concern regarding learning curve and adverse outcomes. Therefore we review and describe our initial experience with bi-cruciate retaining TKA. Methods:. To assess the utility of bi-cruciate retaining TKA, six developer surgeons (Adolph V. Lombardi, Jr. MD, Keith R. Berend MD, Craig J. Della Valle MD, Thomas P. Andriacchi MD, PhD, Jeffrey H. DeClaire MD, Christopher L. Peters MD) treated 383 patients (67% female, mean age 65 years) with primary, cemented bi-cruciate retaining TKA with patella resurfacing between May 2013 and April 2014, and followed them for a minimum of 90 days. After the first 119 cases, the surgeons discussed the adverse outcomes and surgical technique was re-assessed. The frequency of complications prior to and following the change in technique were compared. Results:. The most common complication was intraoperative fracture of the bone island. There were 11 island fractures among the first 119 cases compared to 5 in the subsequent 258 cases (9.2% vs. 1.9%; p = 0.001). There were 4 manipulations performed for range of motion <90 degrees in the first group compared to none in the second group (3.4% vs. 0%; p = 0.003). There were two reoperations overall (0.5%; one for instability and one for tibial loosening), both in the first group. Mean operative time decreased from 82.7 minutes in the first group to 77.5 minutes in the second (p = 0.031). Discussion:. Bi-cruciate retaining TKA may provide a better solution for patients with competent ACLs who are not candidates for partial knee arthroplasty

Partial knee arthroplasty is making a resurgence as many patients and surgeons are realising that there are good options for preserving normally functioning knee tissues when facing end-stage knee OA without having to automatically proceed to TKA. What are potential advantages of this type of reasoning and could “less be more”? Limited comparative data exists comparing the functional results of partial and total knee replacement surgery. This study will report on patient satisfaction and residual symptoms following TKR, fixed bearing PKR, and mobile bearing PKR. What do the patients say when we aren't around?. TKA is not a benign treatment for isolated unicompartmental knee disease. A multicenter study examining 2,919 TKA's and UKA's found lower rates of overall complications at 11% for TKA's and 4.3% for UKA's. Significant variables for TKA included longer length of stay, more patients sent to an ECF, higher manipulation rate, higher readmission, ICU admission, and transfusion rates. Bolognesi, et al examining 68,790 TKA and UKA, reproduced these results with lower DVT/PE, deep infection rates and lower death rates. The 1 year and 5 year revision rates were higher for UKA's and have been hypothesised to be lower thresholds for revision of dissatisfied UKA vs a TKA with well-fixed implants. Functional improvements may be better for UKA vs TKA further substantiating the evidence that “less is more” for the surgical treatment of isolated compartmental disease of the knee. We conducted a multicenter independent survey of 1,263 patients (age 18–75) undergoing primary TKR and PKR for non-inflammatory knee DJD. We examined 13 specific questions regarding pain, satisfaction, and residual symptoms after knee arthroplasty. An independent third party (University of Wisconsin Survey Center) collected data with expertise in collecting healthcare data for state and federal agencies. Multivariate analysis was conducted, significance was set at p<0.05 and adequate power >0.8 was achieved. We controlled for gender, age, income, minority status, and surgical location in the multivariate analysis. Univariate analysis revealed PKR patients were more likely to be younger, male, and have an income greater than $25,000 than TKR patients. Multivariate analysis showed that mobile bearing PKR patients were 1.81 times more likely to report that their operative knee felt “normal” (p = 0.0109) and 2.69 more likely to report satisfaction with ability to perform activities of daily living than TKR recipients (p = 0.0058). Mobile bearing PKR patients were 44% less likely to report grinding/popping/clicking in the knee (p = 0.0142), 39% less likely to report knee swelling (p = 0.0351), and 40% less likely to report knee stiffness in the last 30 days (p = 0.0167) compared to TKR's. Fixed bearing PKR patients were 51% less likely to experience problems getting in and out of a car compared to TKR patients (p = 0.0129). Fixed bearing PKR's were 60% less likely to be satisfied with the degree of pain relief than TKR (p = 0.0113). The remaining questions revealed a trend for advantages in all categories for the MB-PKR compared to TKR but did not reach statistical significance. This study demonstrated that patient satisfaction is higher for MB-PKR than TKR with patients more likely reporting the knee to feel normal and that they were more able to perform activities of daily living. Fixed bearing devices were slightly more likely to report less pain relief than TKR. Mobile bearing partial knee replacement had fewer residual symptoms than fixed bearing PKR

INTRODUCTION. Navigation systems have proved allowing performing measurement of the lower limb axis with a good accuracy, but the mandatory use of reference pins or screws limit their use to the operating room. The use of non-invasive navigation systems has been suggested to overcome this limitation. We conducted a prospective study to assess the validity of such a measurement system with non-invasive fixation of the reference arrays. The main goal was to compare this method with a standard, invasive navigation system requiring bony fixation of the arrays. The following hypothesis was tested: there will be a significant difference between the simultaneous measurement of the mechanical femoro-tibial angle by a standard navigation system and by the non-invasive navigation system. MATERIAL AND METHODS. 20 patients scheduled for total or partial knee arthroplasty were included after giving their informed consent. There were 7 men and 13 women with a median age of 65 years (range, 55 to 90). The median coronal deformation measured by X-rays was 8° of varus (range, 5° valgus to 22 ° varus). The same navigation system was used for both invasive and non-invasive measurements, but the basic algorithms were adapted for the non-invasive technique. For the non-invasive technique, metallic plates were strapped on the thigh and the calf to allow arrays fixation (fig. 1). Coronal femoro-tibial mechanical angle (CMFA) in maximal extension without stress was recorded by the non invasive system. This non-invasive analysis was immediately followed by surgery, and the same angle was measured intra-operatively with the invasive system. Comparisons between non-invasive and invasive measurements were performed using a Wilcoxon test, after checking that their distribution followed a normal distribution, and an equivalence testing with limits of ±3°. The correlation between the two sets of measurements was analyzed using a correlation test Spearman rank. The analysis of the concordance of the two sets of measurements was performed using Bland and Altman tests. The significance level p was set at 0.05. RESULTS. There was no significant difference between non invasive and invasive measurements of the CMFA in full extension. There was a good correlation (fig. 2) and a good concordance (fig. 3) between both measurements. DISCUSSION. The non invasive measurement technique system seems to be as accurate as conventional, invasive navigation. CONCLUSION. This technique might be a valuable alternative to long leg x-rays, with a good accuracy but without radiation exposure. For any figures or tables, please contact the authors directly

It is a not so uncommon clinical scenario: well-fixed, well-aligned, balanced total knee arthroplasty with continued pain. However, radiographs also demonstrate an unresurfaced patella. The debate continues and the controversy remains as whether or not to routinely resurface the patella in total knee arthroplasty. In perhaps the most widely referenced article on the topic, the overall revision rates were no different between the resurfaced (9%) and the unresurfaced (12%) groups and thus their conclusion was that similar results can be obtained with and without resurfacing. However, a deeper look in to the data in this study shows that 4 times more knees in the unresurfaced group were revised for patellofemoral problems. A more recent study concluded that selectively not resurfacing the patella provided similar results when compared to routinely resurfacing. The study does emphasise however, that this conclusion depends greatly on femoral component design and operative diagnoses. This suggests that selective resurfacing with a so-called “patella friendly” femoral component in cases of tibio-femoral osteoarthritis, is a safe and effective strategy. Finally, registry data would support routine resurfacing with a 2.3 times higher relative risk of revision seen in the unresurfaced TKA. Regardless of which side of the debate one lies, the not so uncommon clinical scenario remains; what do we do with the painful TKA with an unresurfaced patella. Precise and accurate diagnosis of the etiology of a painful TKA can be very difficult, and there is likely a strong bias towards early revision with secondary patellar resurfacing in the painful TKA with an unresurfaced TKA. At first glance, secondary resurfacing is associated with relatively poor outcomes. Correia, et al. reported that only half the patients underwent revision TKA with secondary resurfacing had resolution of their complaints. Similarly, only 53% of patients in another series were satisfied with the procedure and pain relief. The conclusions that can be drawn from these studies and others are that either routine patellar resurfacing should be performed in all TKA or, perhaps more importantly, we need to better understand the etiology of pain in an otherwise well-aligned, well-balanced, well-fixed TKA. It is this author's contingency that the presence of an unresurfaced patella leads surgeons to reoperate earlier, without truly identifying the etiology of pain or dissatisfaction. This strong bias; basically there is something more that can be done, therefore we should do it, is the same bias that leads to early revision of partial knee arthroplasty. While very difficult, we as knee surgeons should not revise a partial knee or secondarily resurface a patella due to pain or dissatisfaction. Doing so, unfortunately, only works about half the time. The diagnostic algorithm for evaluating the painful, uresurfaced TKA includes routinely ruling out infection with serum markers and an aspiration. Pre-arthroplasty radiographs should be obtained to confirm suitability and severity of disease for an arthroplasty. An intra-articular diagnostic injection with Marcaine +/− corticosteroid should provide significant pain relief. MARS MRI may be beneficial to evaluate edema within the patella. Lastly, operative implant stickers to confirm implant manufacturer and type are critical as some implants perform less favorably with unresurfaced patellae. To date, no studies of secondary resurfacing describe the results of this, or similar, algorithms for defining patellofemoral problems in the unresurfaced TKA and therefore it is still difficult to conclude that poor results are not simply due to our inherent bias towards early revision and secondary resurfacing of the unresurfaced patella

Patient expectations have escalated over the past several decades with respect to demand for success with total knee arthroplasty (TKA). It is reported that 15 to 20% of TKA recipients are unsatisfied with their result. Dynamic fluoroscopic studies and gait analyses have demonstrated that patients with TKA do not exhibit normal kinematics. On the other hand, patients with partial knee arthroplasty demonstrate more normal kinematics, thought to be secondary to retention of the anterior cruciate ligament (ACL) along with the posterior cruciate ligament (PCL). While not a new concept, bi-cruciate retaining designs in TKA that preserve the natural ligament structure of the knee are drawing renewed interest as an option for patients with higher and more complex activity demand. These designs may result in a more natural kinematic feel as perceived by the patient. This surgical demonstration will outline patient selection criteria and illustrate the technique for performing ACL- and PCL-preserving, bi-cruciate retaining TKA

Yes the paradigm is changing!!!. Refinement of surgical techniques, anesthesia protocols, and patient selection has facilitated this transformation to same day discharge for arthroplasty care. The trend for early discharge has already happened for procedures formerly regarded as “inpatient” procedures such as upper extremity surgery, arthroscopy, ACL reconstruction, foot and ankle procedures, and rotator cuff repair. Our program began focused on Partial Knee Arthroplasty (PKA) and has now expanded to primary TKA and THA, and select revision cases. Over the past few years we have performed: 138 TKA, 111 THA, 244 Partial KA, 6 RevTKA, and 6 RevTHA with no readmissions for pain control. With preoperative Hgb above 11 combined with Tranexamic Acid we have had no transfusions. Medical optimization is critical to the safety and success of patient selection for same day discharge. We utilise a standardised format for preadmission testing. The program centers on the patient, their family, home recovery, preoperative education, efficient surgery, and represents a shift in the paradigm of arthroplasty care. It can be highly beneficial to patients, surgeons, anesthesia, facility costs, and payors as arthroplasty procedures shift to the outpatient space

Patients presenting with arthrosis following high tibial osteotomy (HTO) pose a technical challenge to the surgeon. Slight overcorrection during osteotomy sometimes results in persisting medial unicompartmental arthrosis, but with a valgus knee. A medial UKA is desirable, but will result in further valgus deformity, while a TKA in someone with deformity but intact cruciates may be a disappointment as it is technically challenging. The problem is similar to that of patients with a femoral malunion and arthrosis. The surgeon has to choose where to make the correction. An ‘all inside’ approach is perhaps the simplest. However, this often means extensive release of ligaments to enable ‘balancing’ of the joint, with significant compromise of the soft tissues and reduced range of motion as a consequence. As patients having HTO in the first place are relatively high demand, we have explored a more conservative option, based upon our experience with patient matched guides. We have been performing combined deformity correction and conservative arthroplasty for 5 years, using PSI developed in the MSk Lab. We have now adapted this approach to the failed HTO. By reversing the osteotomy, closing the opening wedge, or opening the closing wedge, we can restore the obliquity of the joint, and preserve the cruciate ligaments. Technique: CT based plans are used, combined with static imaging and on occasion gait data. Planning software is then used to undertake the arthroplasty, and corrective osteotomy. In the planning software, both tibial and femoral sides of the UKA are performed with minimal bone resection. The tibial osteotomy is then reversed to restore joint line obliquity. The placing of osteotomy, and the angling and positioning in relation to the tibial component are crucial. This is more important in the opening of a closing wedge, where the bone but is close to the keel cut. The tibial component is then readjusted to the final ‘Cartier’ angle. Patient guides are then made. These include a tibial cutting guide which locates both the osteotomy and the arthroplasty. At operation, the bone cuts for the arthroplasty are made first, so that these cuts are not performed on stressed bone. The cuts are not in the classical alignment as they are based upon deformed bone so the use of patient specific guides is a real help. The corrective osteotomy is then performed. If a closing wedge is being opened, then a further fibular osteotomy is needed, while the closing of an opening wedge is an easier undertaking. Six cases of corrective osteotomy and partial knee replacement are presented. In all cases, the cruciates have been preserved, together with normal patello-femoral joints. Patient satisfaction is high, because the deformity has been addressed, restoring body image. Gait characteristics are those of UKA, as the ACL has been preserved and joint line obliquity restored